1. Field of the Invention
The present invention relates to rotatable drive arrangements, and more particularly to rotatable drive arrangements in which a driven portion of the arrangement is selectively engaged with or disengaged from a drive portion of the arrangement.
2. History of the Prior Art
There are various situations in which a rotatable drive coupler mechanism must be provided in which a driven portion or coupler thereof can be uncoupled from a drive portion or coupler thereof. The requirement therefor may occur, for example, where a subassembly which is installed in and rotatably driven by a machine must be removable from the machine.
One example of an arrangement requiring a rotatable drive coupler mechanism which must be disengageable is provided by a co-pending application of Lundie et al, Ser. No. 546,834, filed Oct. 31, 1983 and commonly assigned with the present application. The Lundie et al application describes a vacuum seed meter for metering or dispensing seeds therefrom during a planting operation. The vacuum seed meter is coupled to the base of a seed hopper which in turn is mounted on a planting unit. The seed hopper is capable of containing a quantity of seeds to be metered. The seed meter contains a seed disk which is rotatably driven during operation thereof. Rotatable driving of the seed disk is accomplished by coupling a planter drive train to the seed disk within each seed meter.
In seed meters of the type described in the Lundie et al application, it is periodically necessary that the seed hopper and the attached seed meter be removed from the planting unit for various purposes including opening of the seed meter to change the seed disk therein or to clean out the inside of the seed disk or the hopper. For this reason a drive coupler mechanism must be provided which couples the planter drive train to the seed meter when the seed hopper and seed meter are mounted on the planter frame and which uncouples the seed meter from the planter drive train to permit removal of the seed hopper and the seed meter.
One example of a disengageable drive coupler mechanism for use with a seed meter is described in U.S. Pat. No. 3,982,670 of Brass. The drive coupler mechanism in the Brass patent couples the planter drive train to the seed meter in disengageable fashion with an arrangement which spring biases a cylindrical sleeve into engagement with a drive shaft pin to maintain coupling therebetween. The resistance of the spring bias may be overcome to disengage the sleeve from the pin to provide uncoupling of the seed meter from the planter drive train. Both coupling and uncoupling must be done by hand which is inconvenient and time consuming. Such requirement for manual manipulation is particularly disadvantageous in those planters where the planting units and their included seed hoppers and seed meters must be placed relatively close to one another to achieve narrow row to row spacing. In such arrangements the small amount of space between planting units may make it very difficult if not impossible to manually effect coupling and uncoupling using an arrangement such as that described in the Brass patent when a seed meter and its associated hopper are removed or installed.
In drive coupler units using pairs of engaging pins, any radial misalignment of the drive and driven shafts results in a speed change. When the shafts are misaligned, only one pin is driving at a time. During the transition between pins, there is a dead spot in which one pin slides until the other pin engages.
In the case of the planter described in the previously referred to co-pending application of Lundie et al, the seed hopper and attached seed meter may have to be removed under circumstances which premit little if any lateral movement of the seed meter or coupler mechanism in the direction of the axis of a drive gear or other drive member forming part of the planter drive train. Instead, removal and installation of the hopper and seed meter may require essentially movement in a radial direction relative to the drive gear. This places further demands on the drive coupler mechanism, particularly if such mechanism is to be capable of automatic engagement and disengagement without the need for manual assistance. Moreover, such a drive coupler mechanism would have to be capable of automatic connection and disconnection from virtually any rotational position of the driving and driven parts thereof, again without the need for manual assistance. Moreover, such a drive coupler mechanism should be able to tolerate a small amount of axial and radial misalignment between the driving and driven portions thereof to allow for tolerances in mounting the seed hopper and its included seed meter.